Oil Change Frequency

[sailorboy1]

The Yanmar manual says I'm suppose to change the engine oil every 150 hours and the filter every 300 hours. Till I started cruising it mattered little and I replaced both each Spring at launch. But now I'm a cruiser and I motor more and I've also switched to full synthetic oil.

Currently I have 130 hours since last oil and filter change and it's been 4 months. So it's getting near the 150 hours, but I'm questioning the need to change the oil that often now with the synthetic oil. I'm thinking it reasonable to change the oil and filter every 300 hours or yearly whichever happens first.

Yes it seems crazy to risk an engine over an oil change. But am I really risking the engine given the synthetic oil doesn't break down the way regular oil does and since I motor a fair amount it probably doesn't really collect moisture. Plus there's the hassle and disposal issues.

What are other cruisers using synthetic oil doing and/or general thoughts?

[Diesel Bill]

The synthetic oils can go longer than standard dino oil, though some use dino oil as a base stock. The only problem I see is oil dilution from combustion gasses and carbon. These things can and will slowly wear away bearing babbit and if left long enough will become acidic and acid etch soft bearing material. I see no problem with 300 hours or annual oil and filter changes.

[Nineteen]

I would agree with Diesel Bill. Annual or 300hrs would be reasonable - particularly if using the engine regularly and making sure it gets to full normal operating temperature.
If the oil doesnt get hot enough sludge and acids will be the biggest threat.

Cheers Tom

[sailorboy1]

Bump

But I’m still thinking double the recommended hours for Dino oil to be reasonable.

On the other hand I changed the generator oil today and it is using the same synthetic oil and after only 35 hours it was pretty dirty looking (doesn’t have a filter)

[Nineteen]

Hi
All you can do is try the longer interval. If the filter has enough surface area in the media it may cope happily with the extra duty. To be certain oil analysis is the only way.

How quickly an oil changes colour in use depends on many things. How much of the old oil was not drained, how much wear in the cylinder bore (blowby) is allowing combustion byproducts to get into the oil, how hot the oil gets, how much detergent is in the oil to both remove the contaminants and carry them until they are removed by the filter or by draining the oil. These are just a few of the considerations when looking at colour.

Non and low detergent oils look great for a long time because they dont pick up contaminants and allow them to be deposited inside the engine. One of the issues when going to a high quality oil is that they invariably have a better additive package and this usually means more detergents. This will mean an increase in the flushing of deposits, certainly in the short term after swapping, which may actually dictate keeping the standard service interval until things settle down.

300 hours at 60km/h equalls roughly 18000km and that is a long time in a vehicle between services.

Cheers Tom

[Sailmonkey]

Our kubota engine manual allows us to change the oil every 200 hours....I extend it to 250.

There is a new bulletin from kubota engine America that allows for a 750 hour change interval with our engine when used in light plants.

I’m considering going to 300 hours for our propulsion engine unless I’m doing something stupid with it.

[malbert73]

Originally Posted by sailorboy1

Bump

But I’m still thinking double the recommended hours for Dino oil to be reasonable.

On the other hand I changed the generator oil today and it is using the same synthetic oil and after only 35 hours it was pretty dirty looking (doesn’t have a filter)

You have new engines? I’ve heard of a few horror stories with changing to synthetic oil in engines designed for conventional...

[Tellie]

Oil is the life blood of any engine. So 300 hrs or once a year, one filter and four quarts of oil. Or 150 hours twice a year, two filters eight quarts of oil. About $100 bucks and two hours of time a year for possibly a 10+K engine and about 10K to install it. Really?

[flyingfin]

Typical V8 police vehicle

100 hours at 55 mph (2,000 rpm) = 5,500 miles
100 hours at 80 mph (3,000 rpm) = 8,000 miles

We change police vehicle oil every 4,000 miles, they idle a lot and stay hot, then run hard........Kinda like your boat engine

[JC Reefer]

Originally Posted by Tellie

Oil is the life blood of any engine. So 300 hrs or once a year, one filter and four quarts of oil. Or 150 hours twice a year, two filters eight quarts of oil. About $100 bucks and two hours of time a year for possibly a 10+K engine and about 10K to install it. Really?

I have to agree with Tellie. Seems silly to over extend the Manuel recommendations. Just sounds like trouble down the road.

[Wotname]

Originally Posted by sailorboy1

........
On the other hand I changed the generator oil today and it is using the same synthetic oil and after only 35 hours it was pretty dirty looking (doesn’t have a filter)

IMO, any engine without an oil filter needs very frequent oil changes, it is the only to remove the contaminants that would otherwise be caught in a filter. I note however, some (many?) engines without oil filters are considered to be "disposable".

[transmitterdan]

The only reliable way to come up with your own oil change protocol is to perform oil analysis regularly. Big trucking companies use oil analysis results to guide them in setting oil change intervals as well as other engine maintenance scheduling..

[Dockhead]

Originally Posted by sailorboy1

Bump

But I’m still thinking double the recommended hours for Dino oil to be reasonable.

On the other hand I changed the generator oil today and it is using the same synthetic oil and after only 35 hours it was pretty dirty looking (doesn’t have a filter)

What makes you think you can go longer with synthetic at all?

You are assuming that breaking down of the oil is the limiting factor. But it is not -- quality mineral oil should be good for 300 or 400 hours in a low heat, low stress application like this; synthetic for double or triple that -- talking about the oil itself breaking down and losing lubrication.

But the oil breaking down is not the limiting factor at all -- it's soot and other contamination. And here synthetic oil can't old a bit more soot in it than dino juice. Now how much soot gets into the oil also varies according to what kind of engine it is, whether it is common rail or not (much less soot), how worn the rings and bores are, how you are running it, and how much sulfur is in the fuel. But for our engines, which are not common rail, 100 hours is about time, in my opinion, and I would never go over 150 hours.

You just don't need the extra durable film strength of synthetic in a low stress, cool running diesel like a yacht engine. Synthetic oil, in our engines, in the best case, is just a waste of money; in the worst case will harm your engine by giving you the false impression that you can go longer between changes. It might even harm your engine in other ways, look here:

Oil for yacht engines – Cox Engineering

Cox is a yachtsman and professional lubrication engineer -- worth paying attention to what he says.

The maker's specification for oil for your engine is not a joke. The engine was built with a particular kind of oil in mind. You should use exactly that, and nothing else. If your engine can deal with synthetic OK, then fine -- and Yanmar DOES specify synthethic for SOME of their engines. If Yanmar does NOT specify synthetic for your engine, then you shouldn't use it -- they don't do it for a reason.

[sailorboy1]

Originally Posted by Dockhead

But the oil breaking down is not the limiting factor at all -- it's soot and other contamination.

If that is really the case explain why the manufacturer says to replace the oil every 150 hours, but the oil filter every 300 hours.

[Dockhead]

Originally Posted by sailorboy1

If that is really the case explain why the manufacturer says to replace the oil every 150 hours, but the oil filter every 300 hours.

Filter doesn't take out soot!! Or acid!


"Soot is the largest component of contaminants found in the diesel engine lubricating oil. The soot enters lubricating oil mainly through thermophoretic deposition on the cylinder wall. Although the mechanism is still not fully understood, it is generally accepted that soot particles promote engine wear, reducing engine component service life, fuel efficiency and performance. This problem will be further exacerbated when more and more diesel engines use EGR to reduce NOx emissions and when lubricating oil consumption is drastically reduced to control particulate emissions.In this study, lubricating oil samples were taken from 7 different operating diesel engines. The size distribution and concentration of the diesel soot particles in the lubricants were investigated by methods of photosedimentation and quantitative spectrophotometry. The size distributions were compared to those of soot particles in the exhaust. It was found that the mass weighted median diameter of soot particles in the lubricating oil varies from 0.12 to 0.27 μm, and the geometrical standard deviation from 2.4 to 4.0, largely dependent on the type of the engines. The soot size distribution in the oil is in general similar to that in the exhaust. For a single cylinder diesel engine, soot particles were found entering the lubricating oil at a rate of approximately 4% of the total dry exhaust particulate mass emission rate, which in turn is about 0.1% of the fuel mass consumed."

https://www.sae.org/publications/tec...ontent/912344/


Typical diesel oil filter is 10 microns nominal, so will do practically nothing to soot particles of 0.12 to 0.27 microns.

According to this, 100kg of fuel burned (about 25 gallons?) will produce 100 grams of abrasive soot, of which 4 grams will end up in your oil, according to this, but the amount will vary a lot depending on how the engine is used and how worn it is. But that's a bunch of soot!! 100 hours on my engine is about 400kg of fuel, so 16 grams of soot? Ick! Got to get the soot out of the engine oil, and only way to do that is to change it. Using synthetic oil does nothing for this problem.